BACKGROUND: Acute generalized exanthematous pustulosis (AGEP) is a rare pustular severe cutaneous adverse reaction. Differentiating between AGEP and pustular psoriasis may represent a diagnostic challenge. We sought to evaluate the prevalence of comorbidities in a series of patients with AGEP compared to a series of patients with psoriasis vulgaris and to a series of patients with drug-related psoriasis. METHODS: Medical records of 14 patients with AGEP, 33 patients with psoriasis vulgaris, and 18 patients with drug-related psoriasis were reviewed. The presence of comorbidities was recorded, and a comparative analysis was performed. RESULTS: A personal history of psoriasis was present in 4 (28%) patients with AGEP compared to 12 (66%) patients with drug-related psoriasis (Pv=0.03). The prevalence of psoriasis-related morbidities was significantly lower in the AGEP group compared to the psoriasis group and to the drug-related psoriasis group (Pv<0.01, 0.05, respectively). Each of the psoriasis-related morbidities had significantly lower prevalence in the AGEP group compared to the psoriasis group and to the drug-related psoriasis group (Pv<0.01). CONCLUSIONS: In conclusion, differences between AGEP, psoriasis vulgaris, and drug-related psoriasis regarding the prevalence of psoriasis-related morbidities may assist differentiation in borderline cases.